What is Bluetooth Low Energy?

In 1999, a new standard technology for wireless communication by radio waves emerged, known as Bluetooth. Over time, it has been developping further in order to become part of many of our daily devices. Only ten years later, Bluetooth Low Energy (BLE) appeared with the release of version 4.0 of the Core Specification. It provides the same features as its elder brother, but has been optimized in order to reduce energy consumption.

Bluetooth Low Energy features and operational mode

Bluetooth Low Energy is famous under many names: BLE, Bluetooth LE or Bluetooth Smart, its registered trademark. Originally, it has been designed by Nokia under the name of Wibree before being finally implemented by the GIS (Bluetooth Special Interest Group). Its implementation primary objective was to optimize energy consumption. The BLE technology provides an easy and a reliable interface, which is highly appreciated by consumer electronics manufacturers, mobile application developers and engineers. It has become increasingly suitable for all matters related to the Internet of Things (IoT), which is a fast growing industry nowadays.

Features

The main strength of Bluetooth Low Energy is undoubtedly its very low energy consumption. Designed for periodic transfer of little amounts of short-range data, the BLE technology is easy to deploy. It usually consumes only half as much as Bluetooth. Finally, it remains cost-effective with a significant battery lifespan.

Operational mode

There are different types of connections available for the BLE device. A BLE connected item may have up to 4 different functions:

• The "Broadcaster" shall be used as a server. Thus, its purpose is to transfer data to a device on a regular basis, but it does not support any incoming connection.

• The "Observer": In a second step, the device may only monitor and read the data sent by a "broadcaster". In such a case, the object is not able to send any connection to the server.

• The "Central" usually consists of a smartphone or tablet. This device provides two different types of connection: either in advertising mode or in connected mode. It is leading the overall process as it triggers data transfer. - Discover 5 applications to connect your BLE- Tags

• The "Peripheral" device allows connections and data transfer with the ¨Central¨ on a periodical basis. This system´s goal is to ensure universal data transmission by using the standard process, so that other devices also may read and understand the data.

Bluetooth Low Energy operation

Classical Bluetooth Vs BLE technologies

Both technologies actually have very different purposes. Conventional Bluetooth is suitable to process, transfer and exchange a large amount of data on a non-stop basis (example in audio). However, it consumes a lot more power and is much more expensive.

The BLE technology, on the other hand, is suitable for applications that do not require the transfer of large amounts of data, and may therefore recover only a few information (such as time or temperature, for instance). As a result, the device may run on battery for several years at a lower cost than Bluetooth, as it does not require a continuous connection.

Advertising and online modes

Bluetooth devices transmit blocks to allow the broadcasting of data: this is called Advertising. These are 31-byte blocks that may contain sender-specific information. They are also used to connect other devices (usually scanners). Several types of Advertising packages exist, in order to offer a wide range of different functionalities (used for Direct or Indirect Advertising with or without connection available).

BLE enables the connections of two devices, based on the master/slave principle. This defines the online mode. In such cases, GATT protocol is frequently used (acronym for "Generic ATTribute") for data transmission. This protocol defines how two BLE devices interact to exchange data. Both concepts of "services and features" enable to describe the shared information:

• A service may include a series of features
• A feature includes a description, a value and information to define its value.

Some frequencies of Bluetooth 4.2 are dedicated to Advertising while others are specific to the online mode.

Bluetooth allows a bidirectional data transfer using UHF radio waves and operating on the 2.4 GHz band. There are 40 physical channels allocated for time and frequency multiplexing, each of which is located 2 MHz apart from the other (i.e. from 2.4 GHz to 2.8 GHz). Some channels are used for Bluetooth Advertising while some others have been designed for connection purposes.

Bluetooth uses the same frequency range as Wi-Fi but there is no more similarity. Bluetooth and especially the BLE technology uses less power. However, both the range and the speed are significantly lower than in the case of Wi-Fi.

BLE strengths

Each protocol has strengths and weaknesses. Here are some of the BLE strengths:

• From a user perspective: It has been developed by a consortium of industry giants (IBM, Microsoft, Intel, etc.), which indeed guarantees its popularity and high level of economic stability. It is already integrated in all smartphones, for an easier deployment.
• From a security perspective: the protocol allows to manage multiple levels of security.

To remember

Bluetooth Low Energy (BLE) is an industry specific technology allowing a fast transfer of low-consuming data such as temperature, humidity or movement. All this whilst ensuring a twice longer battery lifespan than conventional Bluetooth technologies.